Method and apparatus of accessing channel in wireless communication system

ABSTRACT

A method is provided for accessing a channel in a wireless local area network. A device receives an operation element to set up an operating channel from an access point (AP). The operation element includes a channel type field, a first frequency segment field and a second frequency segment field. The channel type field indicates a use of two 80 MHz channels. The first frequency segment field indicates a center frequency of a primary 80 MHz channel. The second frequency segment field indicates a center frequency of a secondary 80 MHz channel. is obtained based on activities on a part of the primary 80 MHz channel. The device determines whether the secondary 80 MHz channel was idle during an interval immediately preceding the start of the TXOP only after a transmission opportunity (TXOP) is obtained.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. application Ser.No. 14/141,214 filed on Dec. 26, 2013, which is a continuation of U.S.application Ser. No. 13/191,041 filed on Jul. 26, 2011 (now U.S. Pat.No. 8,644,281 issued on Feb. 4, 2014), which claims the benefit under 35U.S.C. §119(e) to U.S. Provisional Application Nos. 61/450,626 filed onMar. 9, 2011, 61/431,441 filed on Jan. 11, 2011, and 61/367,876 filed onJul. 27, 2010, all of which are hereby expressly incorporated byreference into the present application.

BACKGROUND OF THE INVENTION

The present invention relates to a wireless communication, and moreparticularly, to a method and apparatus of accessing a channel in awireless communication system.

With the advancement of information communication technologies, variouswireless communication technologies have recently been developed. Awireless local area network (WLAN) is a technology whereby superhigh-speed internet access is possible in a region providing a specificservice by using a portable terminal such as a personal digitalassistant (PDA), a laptop computer, a portable multimedia player (PMP),etc.

Ever since the institute of electrical and electronics engineers (IEEE)802, i.e., a standardization organization for WLAN technologies, wasestablished in February 1980, many standardization works have beenconducted. Initially, WLAN used a frequency of 2.4 GHz to support a datarate of 1 to 2 Mbps by using frequency hopping, spread spectrum,infrared ray communication, etc. Recently, the WLAN can support a datarate of up to 54 Mbps by using orthogonal frequency divisionmultiplexing (OFDM). In addition, the IEEE 802.11 is developing orcommercializing standards of various technologies such as quality ofservice (QoS) improvement, access point (AP) protocol compatibility,security enhancement, radio resource measurement, wireless access invehicular environments, fast roaming, mesh networks, inter-working withexternal networks, wireless network management, etc.

The IEEE 802.11b standard supports a data rate of up to 11 Mbps (bitsper second) by using a frequency band of 2.4 GHz. The IEEE 802.11astandard uses a frequency band of 5 GHz instead of the frequency band of2.4 GHz and thus significantly reduces influence of interference. TheIEEE 802.11a standard has improved the data rate to up to 54 Mbps byusing the OFDM technology. The IEEE 802.11a standard uses a 20 MHzchannel bandwidth within a bandwidth of 5 GHz. Although there arenational differences, 13 channels can be used. The IEEE 802.11n standardprovides increased network speed and reliability, extended coverage. TheIEEE 802.11a standard uses a 20 MHz channel bandwidth or a 40 MHzchannel bandwidth within a bandwidth of 5 GHz.

Basic access mechanism of an IEEE 802.11 is a carrier sense multipleaccess with collision avoidance (CSMA/CA) combined with binaryexponential backoff. The CSMA/CA mechanism is also referred to as adistributed coordinate function (DCF) and basically employs a “listenbefore talk” access mechanism. A station (STA) listens to a wirelessmedium before starting transmission. As a result of listening, if it issensed that the wireless medium is not in use, the listening STA startsits transmission. Otherwise, if it is sensed that the wireless medium isin use, the STA does not start its transmission but enters a delayduration determined by the binary exponential backoff algorithm. TheCSMA/CA channel access mechanism is not so efficient since throughput atthe MAC layer provides only 50 to 60% of throughput at the physicallayer.

IEEE 802.11 VHT (Very High Throughput) is one of WLAN systems which havebeen recently proposed to support throughput of higher than 1 Gbps. Twokinds of VHT system are independently progressed: one is IEEE 802.11acbelow 6 GHz band and another is IEEE 802.11ac for 60 GHz band. In orderto support throughput of higher than 1 Gbps, a feasibility test for 8×8multiple-input multiple-output (MIMO) and 80 MHz channel bandwidth hasbeen progressed. The VHT system is expected to use channel bandwidthsbroader than at least 80 MHz. The 80 MHz channel bandwidths can beconfigured by combining at least four adjacent 20 MHz channel. An APsimultaneously transmits data at different frequencies to multiple STAsto increase the overall throughput.

Meanwhile, IEEE 802.11y is an IEEE 802.11 amendment for operating theIEEE 802.11 between 3650 MHz and 3700 MHz. The IEEE 802.11y providesseveral key features such as contention based protocol (CBP), extendedchannel switch announcement (ECSA), and dependent station enablement(DSE). The extended channel switch announcement provides a mechanism foran access point to notify the stations connected to it of its intentionto change channels or to change channel bandwidth. This mechanism willallow for the WLAN to continuously choose the channel that is the leastnoisy and the least likely to cause interference. This mechanism willalso be used in the IEEE 802.11n, which will allow devices to switchbetween the IEEE 802.11y operation and the IEEE 802.11n operation in the2.4 GHz and 5 GHz bands. The extended channel switch announcement alsoprovides switching of a regulatory class. The regulatory class definesoperating frequency band, transmit power limitation, etc.

The multi-band supporting protocol described above can be an essentialfeature of the VHT system. For the VHT system, the ECSA provided by theIEEE 802.11y needs to be enhanced. That is, for the VHT system whichuses channel bandwidths broader than at least 40 MHz, a method ofallocating and changing channel set is required. Also, a technique forefficiently operating a wideband VHT system is required.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus of accessing achannel to support wideband in a WLAN system.

In an aspect, a method of accessing a channel in a wireless local areanetwork is provided. The method includes receiving, by a device, anoperation element for setting up or switching at least one channel froman access point (AP), the operation element including a channel typefield indicating whether the at least one channel is either a singlechannel or multiple channels, and the operation element including twochannel center frequency segment fields indicating channel centerfrequency of a primary channel and a secondary channel respectively ifthe channel type field indicates that the at least one channel ismultiple channels, determining whether the primary channel is idleduring a first interval, determining whether the secondary channel isidle during a second interval if the primary channel is idle, andtransmitting data by using the primary channel and the secondary channelto the AP or at least one station in a basic service set (BSS) if theprimary channel and the secondary channel are idle.

The at least one channel may be multiple channels if the channel typefield is set to 1.

The primary channel may be not contiguous with the secondary channel.

A bandwidth of the primary channel and the secondary channel may be 80MHz respectively.

The at least one channel may be a single channel if the channel typefield is set to 0.

The single channel may have one of bandwidth of 20 MHz, 40 MHz, 80 MHzand 160 MHz.

The operation element may be included in a channel switch announcementframe which is used by the AP to advertise a channel switch.

The operation element may be included in a beacon frame or a proberesponse frame.

The operation element may be included in a tunneled direct link setup(TDLS) channel switch request frame.

In another aspect, a device for accessing a channel in a wireless localarea network is provided. The device includes a radio frequency (RF)unit configured for transmitting or receiving a radio signal, and aprocessor, coupled to the RF unit, and configured for receiving anoperation element for setting up or switching at least one channel froman access point (AP), the operation element including a channel typefield indicating whether the at least one channel is either a singlechannel or multiple channels, and the operation element including twochannel center frequency segment fields indicating channel centerfrequency of a primary channel and a secondary channel respectively ifthe channel type field indicates that the at least one channel ismultiple channels, determining whether the primary channel is idleduring a first interval, determining whether the secondary channel isidle during a second interval if the primary channel is idle, andtransmitting data by using the primary channel and the secondary channelto the AP or at least one station in a basic service set (BSS) if theprimary channel and the secondary channel are idle.

In another aspect, a device for accessing a channel in a wireless localarea network is provided. The device includes a radio frequency (RF)unit configured for transmitting or receiving a radio signal, and aprocessor, coupled to the RF unit, and configured for transmitting anoperation element for setting up or switching at least one channel to atleast one station in a basic service set (BSS), the operation elementincluding a channel type field indicating whether the at least onechannel is either a single channel or multiple channels, and theoperation element including two channel center frequency segment fieldsindicating channel center frequency of a primary channel and a secondarychannel respectively if the channel type field indicates that the atleast one channel is multiple channels, determining whether the primarychannel is idle during a first interval, determining whether thesecondary channel is idle during a second interval if the primarychannel is idle, and transmitting data by using the primary channel andthe secondary channel to the at least one station in the BSS if theprimary channel and the secondary channel are idle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an exemplary structure of a wirelesslocal area network (WLAN) system to implement an embodiment of thepresent invention.

FIG. 2, including (a), (b) and (c), illustrates exemplary channelmanagement that combines three subchannels to support a bandwidth of 60MHz.

FIG. 3, including (a), (b), (c) and (d), illustrates exemplary channelmanagement that combines four subchannels to support a bandwidth of 80MHz.

FIG. 4 illustrates an exemplary format of an operation element forsetting up multiple channels.

FIG. 5 illustrates an exemplary channel switch announcement frame forchanging a channel.

FIG. 6 illustrates an exemplary extended channel switch announcementframe.

FIG. 7 is a diagram illustrating a flow of messages in a TDLS wirelessnetwork.

FIG. 8 illustrates an exemplary extension channel offset informationelement according to an embodiment of the present invention.

FIG. 9 illustrates an exemplary extension channel offset informationelement according to another embodiment of the present invention.

FIG. 10 illustrates a flowchart according to an embodiment of thepresent invention.

FIG. 11 is a block diagram of a wireless communication system toimplement an embodiment of the present invention is implemented.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic view showing an exemplary structure of a wirelesslocal area network (WLAN) system to implement an embodiment of thepresent invention.

Referring to FIG. 1, the WLAN system includes one or more basis servicesets (BSSs). The BSS is a set of stations (STAs) which are successfullysynchronized to communicate with one another. The BSS can be classifiedinto an infrastructure BSS and an independent BSS (IBSS). Theinfrastructure BSSs (BSS1 and BSS2) shown in FIG. 1 include STAs 10, 30and 40, access points (APs) 20 and 50. The AP is a STA providing adistribution service. The APs 20 and 50 are connected by means of adistribution system (DS). The IBSS operates as Ad-hoc mode and does notinclude any AP. The IBSS constitutes a self-contained network sinceconnection to the DS is not allowed. A plurality of infrastructure BSSscan be interconnected by the use of the DS. An extended service set(ESS) is a plurality of BSSs connected by the use of the DS. In the sameESS, a non-AP STA can move from on BSS to another BSS while performingseamless communication.

The STA is an arbitrary functional medium including a medium accesscontrol (MAC) and wireless-medium physical layer (PHY) interfaceconforming to the institute of electrical and electronics engineers(IEEE) 802. 11 standard. The STA may be an AP or a non-AP STA. A non-APSTA may be a portable terminal operated by a user. The non-AP STA may besimply referred to as an STA. The non-AP STA may be referred to as awireless transmit/receive unit (WTRU), a user equipment (UE), a mobilestation (MS), a mobile terminal, a mobile subscriber unit, etc. The APis a functional entity for providing connection to the DS through awireless medium for an associated STA. Although communication betweennon-AP STAs in an infrastructure BSS including the AP is performed viathe AP in principle, the non-AP STAs can perform direct communicationwhen a direct link is set up. The AP may be referred to as a centralizedcontroller, a base station (BS), a node-B, a base transceiver system(BTS), a site controller, etc.

A very high throughput (VHT) WLAN system aims to be reflected on one ofinternational mobile telecommunication (IMT)-advanced technologiescorresponding to fourth-generation telecommunication standard.Accordingly, the VHT WLAN system is required to operate in IMT-Advancedcandidate bands and the existing 2.4 GHz and 5 GHz bands.

The VHT WLAN system is required to use a bandwidth wider than at least60 MHz in order to secure throughput higher than 1 Gbps. To segment awideband into a plurality of narrowbands and use the narrowbands isefficient more than to use the wideband as a single channel in terms ofbackward compatibility and resource efficiency.

Hereinafter, a narrowband channel having a bandwidth of 20 MHz isreferred to as a subchannel. A technique of binding three or foursubchannels to support a bandwidth of 60 MHz or 80 MHz will now bedescribed. The number of subchannels, the bandwidth of the subchanneland the overall bandwidth are exemplary purpose only.

A bandwidth of 40 MHz can be supported in the IEEE 802.11n using aprimary channel and a secondary channel. A VHT AP may support anextension channel. An extension channel may have at least 40 MHzbandwidth. A VHT STA informs the VHT AP of the availability of asecondary channel and an extension channel. If the VHT STA does notsupport an extension channel, the VHT AP and a high throughput (HT) APoperates in the same manner. If the VHT STA supports an extensionchannel only, and a bandwidth of the extension channel is 40 MHz, theVHT STA can use a bandwidth of 20 MHz, 40 MHz or 60 MHz according to theavailability of the extension channel. If the VHT STA supports both asecondary channel and an extension channel, the VHT STA can use abandwidth of 20 MHz, 40 MHz, 60 MHz and 80 MHz.

FIG. 2, including (a), (b) and (c), illustrates exemplary channelmanagement that combines three subchannels to support a bandwidth of 60MHz.

Referring to FIG. 2, the three subchannels include a primary channel andtwo extension channels. The primary channel is set in order to securebackward compatibility with STAs (hereinafter referred to as legacySTAs) supporting standards of lower than IEEE 802. 11n using a bandwidthof 20 MHz. Legacy STAs supporting 20 MHz use the primary channelpreferentially. STAs supporting 40 MHz or 60 MHz can use the primarychannel, two extension channels and/or a combination thereof

Subfigure (a) of FIG. 2 shows that the extension channels using 20 MHzare located in a frequency band lower than the primary channel. Here,the two 20 MHz extension channels can be set as a single 40 MHzextension channel. Subfigure (b) of FIG. 2 shows that the two extensionchannels are located in a frequency band higher than the primarychannel. The two 20 MHz extension channels can be set as a single 40 MHzextension channel. Subfigure (c) of FIG. 2 shows that the primarychannel is located between the two extension channels.

In (a) and (b) of FIG. 2, the multiple channels can be administrated byusing the primary channel and the single 40 MHz extension channelcontiguous to the primary channel. In (c) of FIG. 2, the multiplechannels can be administrated by the primary channel and two 20 MHzextension channels contiguous to the primary channel.

An AP can set a subchannel among overall available channels as a primarychannel and use the primary channel as a common channel for controlsignal. The AP can set a bandwidth of an extension channel to one of 20MHz, 40 MHz and 60 MHz according to channel availability if a STAsupports the extension channel.

FIG. 3, including (a), (b), (c) and (d), illustrates exemplary channelmanagement that combines four subchannels to support a bandwidth of 80MHz.

Referring to FIG. 3, the four subchannels include a primary channel, asecondary channel and two extension channels. The primary channel andthe secondary channel are set in order to secure backward compatibilitywith legacy STAs supporting standards of lower than IEEE 802.11n using40 MHz. Legacy STAs supporting 20 MHz preferentially use the primarychannel and use the secondary channel when the primary channel is beingused. Legacy STAs supporting 40 MHz preferentially use the primarychannel and the secondary channel. STAs supporting bandwidths higherthan 60 MHz can use the primary channel, the secondary channel, theextension channels and/or a combination thereof.

Subfigure (a) of FIG. 3 shows that the extension channels having 20 MHzare located in a frequency band lower than the primary channel and thesecondary channel. The primary channel is located in the highest bandand the secondary channel is located below the primary channel. Here,the two 20 MHz extension channels can be set as a single 40 MHzextension channel. Subfigure (b) of FIG. 3 shows that the 20 MHzextension channels are located in a frequency band higher than theprimary channel and the secondary channel. The primary channel islocated in the lowest band and the secondary channel is located abovethe primary channel. Here, the two 20 MHz extension channels can be setas a single 40 MHz extension channel. Subfigure (c) of FIG. 3 shows thatthe primary channel and the secondary channel are located between thetwo extension channels. The primary channel is located in a band higherthan the secondary channel. Subfigure (d) of FIG. 3 shows that theprimary channel and the secondary channel are located between the twoextension channels. The primary channel is located in a band lower thanthe secondary channel.

In (a) and (b) of FIG. 3, the multiple channels can be administrated byusing the primary channel, the secondary channel and an extensionchannel having 40 MHz. In (c) and (d) of FIG. 3, the multiple channelscan be administrated by using the primary channel, the secondary channeland two extension channels each having 20 MHz.

FIG. 4 illustrates an exemplary format of an operation element forsetting up multiple channels. An operation element 400 for settingmultiple channels includes an element ID 410, a primary channel field420, a secondary channel offset field 430, an extension channel offsetfield 440 and a channel width field 450. The element ID 410 is anidentifier for identifying the operation element 400. The primarychannel field 420 indicates the position of a primary channel in theavailable bandwidth of a system and can be represented as a channelnumber. The secondary channel offset field 430 indicates the offset ofthe secondary channel relative to the primary channel. The secondarychannel offset field 430 can be configured as represented by Table 1.

TABLE 1 Value Name Description 0 SCN (No Secondary Channel) No secondarychannel is present. 1 SCA (Secondary Channel Above) The secondarychannel is above the primary channel. 3 SCB (Secondary Channel Below)The secondary channel is below the primary channel.

The extension field offset field 440 indicates the position of anextension channel relative to the primary channel and/or the secondarychannel. The value of the extension channel offset field 440 can be setbased on the primary channel, as represented by Table 2.

TABLE 2 Value Name Description 0 ECN (No Extension Channel) Indicatesthat no extension channel is present 1 ECA (Extension Channel Above)Indicates that the extension channels are above the primary channel 2ECB (Extension Channel Below) Indicates that the extension channels arebelow the primary channel 3 ECC (Extension Channel Cross) Indicates thatthe extension channels are cross the primary channel 4-255 Reserved

The channel width field 450 represents a channel bandwidth supported bya STA or a channel bandwidth used for transmission. The STA can supportat least one of bandwidths 20 MHz, 40 MHz, 60 MHz and 80 MHz.

Though Table 2 shows that the extension channel offset field 440indicates the position of the extension channel based on the primarychannel, the extension channel offset field 440 may indicate theposition of the extension channel based on the secondary channel orbased on a combination of the primary channel and the secondary channel.

The terms and values represented in Tables 1 and 2 are exemplary andthose who skilled in the art can easily change the terms and values. Inaddition, all the aforementioned fields are not included in theoperation element 400. Some of the fields may be omitted or other fieldsmay be added. For example, the operation element 400 may not include thesecondary channel offset field 430 if the secondary channel is not used.

The operation element 400 may be included in at least one of a beaconframe, a probe response frame and an association response frame andtransmitted from an AP to a STA. Above frames may be referred to section7.2.3 of IEEE standard P802. 11-REVma/D9.0 “Wireless LAN Medium AccessControl (MAC) and physical layer (PHY) specifications” which is herebyincorporated by reference.

An AP that classifies 60 MHz, 80 MHz or wider bandwidth as a primarychannel, a secondary channel and an extension channel and manages thechannels is required to change a channel previously allocated thereto inconsideration of channel status. For example, if considerable noise isgenerated or/and interference with other signals occurs in a subchannelused as a primary channel in the overall channel bandwidth, anothersubchannel is updated to the primary channel to efficiently manage aWLAN system.

FIG. 5 illustrates an exemplary channel switch announcement frame forchanging a channel.

Referring to FIG. 5, a channel switch announcement frame 500 is used byan AP in a BSS or a STA in an IBSS to advertise when it is changing to anew channel. The channel switch announcement frame 500 includes acategory field 510, an action value field 520, a channel switchannouncement element field 530, a secondary channel offset element field540, and an extension channel offset element field 550. The categoryfield 510 may represent spectrum management. The action value field 520may represent a channel switch announcement frame.

The channel switch announcement element field 530 includes an element ID531, a length field 532, a channel switch mode field 533, a new channelnumber field 535 and a channel switch count field 536. The channelswitch mode field 533 indicates any restrictions on transmission until achannel switch. An AP in a BSS or a STA in an IBSS may set the channelswitch mode field 533 to either 0 or 1 on transmission. The channelswitch mode field 533 set to 1 means that the STA in a BSS to which theframe containing the element is addressed transmits to further frameswithin the BSS until the scheduled channel switch. The channel switchmode field 533 set to 0 does not impose any requirement on the receivingSTA. The new channel number field 535 is set to the number of thechannel to which the STA is moving. The channel switch count field 536either is set to the number of target beacon transmission times (TBTTs)until the STA sending the channel switch announcement element switchesto the new channel or it set to 0. A value of 1 indicates that theswitch shall occur immediately before the next TBTT. A value of 0indicates that the switch occurs at any time after the frame containingthe element is transmitted.

The secondary channel offset element field 540 includes an element ID541, a length field 542 and a secondary channel offset field 543. Thesecondary channel offset element field 540 represents information on anew secondary channel when the secondary channel is changed to the newsecondary channel. The secondary channel offset field 543 may be set asrepresented by Table 1.

The extension channel offset element field 550 includes an element ID551, a length field 552 and an extension channel offset field 553 andrepresents information on a new extension channel when the extensionchannel is changed to the new extension channel. The extension channeloffset field 553 may be set as represented by Table 2.

FIG. 6 illustrates an exemplary extended channel switch announcementframe.

Referring to FIG. 6, an extended channel switch announcement frame 600is used by an AP in a BSS or a STA in an IBSS to advertise when it ischanging to a new channel or a new channel in a new regulatory class.The extended channel switch announcement frame 600 includes a categoryfield 610, an action value field 620, an extended channel switchannouncement element field 630, a secondary channel offset element field640 and an extension channel offset element field 650.

Compared with the channel switch announcement frame 500 in FIG. 5, theextended channel switch announcement frame 600 includes the extendedchannel switch announcement element field 630 which further includes anew regulatory class field 634. The new regulatory class field 634 isset to the number of the regulatory class after the channel switch. Anew channel number field 635 is set to the number of the channel afterthe channel switch. The channel number is a channel from the STA's newregulatory class.

The secondary channel offset element field 640 and the extension channeloffset element field 650 can be set in the same manner in which thesecondary channel offset element field 540 and the extension channeloffset element field 550 of the channel switch announcement frame 500shown in FIG. 5 are set.

Hereinafter, a direct link setup procedure in a TDLS wireless networkwill be described now.

A direct link setup (DLS) between the non-AP STAs supporting Quality ofService (QoS) has been introduced to improve the efficiency of wirelesscommunications. Accordingly, in the BSS supporting the QoS, that is, inthe QBSS including QoS STAs (QSTA) and QoS APs (QAP), the non-AP STAscan set up a direct link therebetween and directly communicate with eachother through the direct link.

A TDLS (Tunneled Direct Link Setup) is a wireless communication protocolnewly suggested to overcome such a limitation regarding the existing DLSservice. The TDLS allows the QSTAs to set up a direct link in thecurrently used WLAN environments in accordance with the IEEE802.11a/b/g. Accordingly, the TDLS defines methods of allowing the QSTAsto set up a direct link even in the BSS managed by the legacy AP.Hereinafter, a wireless network supporting the TDLS method is referredto as a TDLS wireless network.

It can be considered that the direct link setup procedure in the QBSS issimilarly employed as the direct link setup procedure in the TDLSwireless network. According to the direct link setup procedure in theQBSS, the direct link setup procedure is completed by a two-wayhandshake between two QSTAs.

FIG. 7 is a diagram illustrating a flow of messages in a TDLS wirelessnetwork.

The TDLS wireless network system includes at least two non-AP QSTAs(QSTA1 and QSTA2) and a legacy AP not supporting the DLS procedure. Forthe purpose of convenient explanation in the following description, thenon-AP QSTA initiating the direct link setup procedure, that is,transmitting the TDLS setup request frame, is called an initiating QSTAor a TDLS initiator and the non-AP QSTA related to the direct link setupprocedure with the TDLS initiator or setting up a direct link thereto iscalled a peer QSTA.

Referring to FIG. 7, the first QSTA (QSTA1) as the TDLS initiatorintending to set up a direct link to the second QSTA2 as the peer STAtransmits to the second QSTA a request message for requesting forsetting up a direct link (S800). The request message may be a TDLS setuprequest frame. The AP merely relays the request message received fromthe first QSTA to the second QSTA. The second QSTA having received theTDLS setup request frame transmits a response message to the first QSTAin response to the TDLS setup request frame (S810). The response messagemay be a TDLS setup response frame. In this case, the AP merely relaysthe response message received from the second QSTA to the first QSTA.

Hereinafter, a method of accessing a channel in a WLAN according to thepresent invention will be described.

FIG. 8 illustrates an exemplary extension channel offset informationelement according to an embodiment of the present invention.

Referring to FIG. 8, an extension channel offset element field 900includes an element ID 910, a length field 920, a channel type filed930, a channel center frequency segment 1 field 940, and a channelcenter frequency segment 2 field 950. The extension channel offsetelement field 900 may be included in a channel switch announcement framedescribed in FIG. 5 or an extended channel switch announcement framedescribed in FIG. 6. That is, the extension channel offset element field900 may be modification of an extension channel offset element field 550described in FIG. 5 or an extended channel offset element field 650described in FIG. 6. Or, the extension channel offset element field 900may be included the in a beacon frame or a probe response frame.

The channel type field 930 indicates composition of channels, whichindicates that at least one allocated channel is either a single channelor multi-channels. If the channel type field is set to 0, it indicatesthat the at least one allocated channel is a single channel. The singlechannel may have one of a bandwidth of 20 MHz, 40 MHz, 80 MHz and 160MHz. If the channel type field is set to 1, it indicates that at leastone allocated channel are multiple channels. The multiple channels maybe two discontinuous channels, and the two discontinuous channels have abandwidth of 80 MHz respectively.

The channel center frequency segment 1 field 940 may indicate channelcenter frequency for a single channel if the channel type field 930 isset to 0. In this case, the channel center frequency segment 1 field 940may be set to a channel number corresponding to the channel centerfrequency of the single channel. Or, the channel center frequencysegment 1 field 940 may indicate channel center frequency of a segment 1channel in multi-channels if the channel type field 930 is set to 1. Inthis case, the channel center frequency segment 1 field 940 may be setto a channel number corresponding to the channel center frequency of thesegment 1 channel in the multi-channels the single channel.

The channel center frequency segment 2 field 950 may indicate channelcenter frequency of a segment 2 channel in the multi-channels if thechannel type field 930 is set to 1. In this case, the channel centerfrequency segment 2 field 950 may be set to a channel numbercorresponding to the channel center frequency of the segment 2 channelin the multi-channels the single channel. If the channel type field 930is set to 0, the channel center frequency segment 2 field 950 may not bedefined.

Meanwhile, the extension channel offset information element in FIG. 8may be applied to a TDLS wireless network system. The extension channeloffset information element may be included in a TDLS channel switchrequest frame when a switch to an 80 MHz, 160 MHz or 80+80 MHz directlink is indicated. Switching to an 80 MHz/160 Mhz/80+80 MHz off-channeldirect link may be achieved by including the following information inthe TDLS channel switch request frame.

An operating class element indicating 40 MHz channel spacing.

A secondary channel offset element indicating SCA or SCB.

An extension bandwidth channel switch element indicating 80 MHz/160MHz/80+80 MHz channel width.

The operating class has a value of 5 GHz for channel starting frequency.

FIG. 9 illustrates an exemplary extension channel offset informationelement according to another embodiment of the present invention.

Referring to FIG. 9, the first QSTA (QSTA1) as the TDLS initiatorintending to set up a direct link to the second QSTA2 as the peer STAtransmits to the second QSTA a request message for requesting forsetting up a direct link (S1000). The request message may be a TDLSsetup request frame. The AP merely relays the request message receivedfrom the first QSTA to the second QSTA. The second QSTA having receivedthe TDLS setup request frame transmits a response message to the firstQSTA in response to the TDLS setup request frame (S1010). The responsemessage may be a TDLS setup response frame. In this case, the AP merelyrelays the response message received from the second QSTA to the firstQSTA. The first QSTA (QSTA1) as the TDLS initiator intending to switch achannel to an 80 MHz/160 MHz/80+80 MHz direct link as the peer STAtransmits to the second QSTA a request message for requesting forswitching a channel (S1020). The request message may be a TDLS channelswitch request frame. The AP merely relays the request message receivedfrom the first QSTA to the second QSTA.

FIG. 10 illustrates a flowchart according to an embodiment of thepresent invention.

In step S1100, a STA receives an operation element for setting up orswitching at least one channel from an AP. The operation elementincludes a channel type field indicating whether the at least onechannel is either a single channel or multiple channels, and includestwo channel center frequency segment fields indicating channel centerfrequency of a primary channel and a secondary channel respectively ifthe channel type field indicates that the at least one channel ismultiple channels.

In step S1110, the STA determines whether the primary channel is idleduring a first interval. The primary interval may immediately precedesthe time at which a STA is permitted to begin a transmission opportunity(TXPO) and the SGA has at least one MAC service data unit (MSDU) pendingfor transmission for the AC of the permitted TXPO.

In step S1120, the STA determines whether the secondary channel is idleduring a second interval if the primary channel is idle. The secondinterval may immediately precedes the start of the TXOP.

In step S1130, the STA transmits data by using the primary channel andthe secondary channel to the AP or at least one station in a BSS if theprimary channel and the secondary channel are idle.

FIG. 11 is a block diagram of a wireless communication system toimplement an embodiment of the present invention is implemented.

An AP 1200 includes a processor 1201, a memory 1202 and a radiofrequency (RF) unit 1203. The processor 1201 implements a proposedfunction, process and/or method. The memory 1202 is operativelyconnected to the processor 1201 and stores information for operating theprocessor 1201. The RF unit 1203 is operatively connected to theprocessor 1201 and transmits and/or receives RF signals.

A STA 1250 includes a processor 1251, a memory 1252 and an RF unit 1253.The processor 1251 implements a proposed function, process and/ormethod. The memory 1252 is operatively connected to the processor 1251and stores information for operating the processor 1251. The RF unit1253 is operatively connected to the processor 1251 and transmits and/orreceives RF signals.

The processors 1201, 1251 may include application-specific integratedcircuit (ASIC), other chipset, logic circuit and/or data processingdevice. The memories 1202, 1252 may include read-only memory (ROM),random access memory (RAM), flash memory, memory card, storage mediumand/or other storage device. The RF units 1203, 1253 may includebaseband circuitry to process radio frequency signals. When theembodiments are implemented in software, the techniques described hereincan be implemented with modules (e.g., procedures, functions, and so on)that perform the functions described herein. The modules can be storedin memories 1202, 1252 and executed by processors 1201, 1251. Thememories 1202, 1252 can be implemented within the processors 1201, 1251or external to the processors 1201, 1251 in which case those can becommunicatively coupled to the processors 1201, 1251 via various meansas is known in the art.

According to the present invention, an efficient channel access methodcan be provided.

In view of the exemplary systems described herein, methodologies thatmay be implemented in accordance with the disclosed subject matter havebeen described with reference to several flow diagrams. While forpurposed of simplicity, the methodologies are shown and described as aseries of steps or blocks, it is to be understood and appreciated thatthe claimed subject matter is not limited by the order of the steps orblocks, as some steps may occur in different orders or concurrently withother steps from what is depicted and described herein. Moreover, oneskilled in the art would understand that the steps illustrated in theflow diagram are not exclusive and other steps may be included or one ormore of the steps in the example flow diagram may be deleted withoutaffecting the scope and spirit of the present disclosure.

What has been described above includes examples of the various aspects.It is, of course, not possible to describe every conceivable combinationof components or methodologies for purposes of describing the variousaspects, but one of ordinary skill in the art may recognize that manyfurther combinations and permutations are possible. Accordingly, thesubject specification is intended to embrace all such alternations,modifications and variations that fall within the spirit and scope ofthe appended claims.

What is claimed is:
 1. A method for accessing a channel in a wirelesslocal area network, the method comprising: receiving, by a device, anoperation element to set up an operating channel from an access point(AP), the operation element including a channel type field, a firstfrequency segment field and a second frequency segment field, thechannel type field indicating a use of two 80 MHz channels, the firstfrequency segment field indicating a center frequency of a primary 80MHz channel, the second frequency segment field indicating a centerfrequency of a secondary 80 MHz channel, the primary 80 MHz channelbeing not contiguous with the secondary 80 MHz channel; obtaining atransmission opportunity (TXOP) based on activities on a part of theprimary 80 MHz channel; determining, by the device, whether thesecondary 80 MHz channel was idle during an interval immediatelypreceding the start of the TXOP only after the TXOP is obtained; andtransmitting, by the device, data by using the primary 80 MHz channeland the secondary 80 MHz channel to the AP during the TXOP if thesecondary 80 MHz channel was idle.
 2. The method of claim 1, wherein theoperation element is received in a beacon frame.
 3. The method of claim1, further comprising: transmitting, by the device, data by using theprimary 80 MHz channel to the AP during the TXOP if the secondary 80 MHzchannel was not idle.
 4. A device for accessing a channel in a wirelesslocal area network, the device comprising: a radio frequency (RF) unitconfigured to transmit and receive radio signals; and a processoroperatively coupled to the RF unit and configured to: instruct the RFunit to receive an operation element to set up an operating channel froman access point (AP), the operation element including a channel typefield, a first frequency segment field and a second frequency segmentfield, the channel type field indicating a use of two 80 MHz channels,the first frequency segment field indicating a center frequency of aprimary 80 MHz channel, the second frequency segment field indicating acenter frequency of a secondary 80 MHz channel, the primary 80 MHzchannel being not contiguous with the secondary 80 MHz channel; obtain atransmission opportunity (TXOP) based on activities on a part of theprimary 80 MHz channel; determine whether the secondary channel was idleduring an interval immediately preceding the start of the TXOP onlyafter the TXOP is obtained; and instruct the RF unit to transmit data byusing the primary 80 MHz channel and the secondary 80 Mhz channel to theAP during the TXOP if the secondary 80 MHz channel was idle.
 5. Thedevice of claim 4, wherein the operation element is received in a beaconframe.
 6. The device of claim 4, wherein the processor is configured to:instruct the RF unit to transmit data by using the primary 80 MHzchannel to the AP during the TXOP if it is determined that the secondary80 MHz channel was not idle.